In this study we determine the prevalence of pneumococcal nasopharyngeal carriage among children attending day-care centres in and around Oslo, Norway four years after switching from the 7-valent pneumococcal conjugate vaccine (PCV) to the 13-valent PCV. Furthermore, we investigate which variables determine the presence of pneumococcal carriage. The study invited all children attending 40 day care centres. A nasopharyngeal swap was collected together with questionnaire data. The results are compared to data obtained in similar studies performed before widespread childhood vaccination with the pneumococcal conjugate vaccine (PCV; 2006), 2 years after the implementation of vaccination in the childhood vaccination programme (2008) and 2 years after switch from the 7-valent PCV to the 13-valent vaccine (2013). Results are useful for policy making – both, for the childhood vaccination programme as well as for vaccine recommendations for risk groups